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The apostrophe is used most commonly to show possession, as in "Mary's bike" or "the students' poems." For a singular noun, always add 's. An easy way to remember whether to add 's or just ' to a plural noun is to look at the end of the word. If there is already an S present, you do not need to add another:

I met my friend's wife yesterday. (one friend)
I met my friends' wives yesterday. (more than one friend)

The boy's dog is huge. (one boy)
The boys' dog is huge. (more than one boy)

She fought for the woman's rights. (one woman)
She fought for women's rights. (more than one woman, but the plural word does not already end in S. Similar plural nouns are "men" and "children.")

Marcus' car is in the shop. (the name ends in S; there is no reason to add another)
Marcus's car is in the shop. (this usage is gaining popularity, but the added S is still unnecessary)

There is one exception to the above rules:

Its teeth were sharp. (this is the possessive form)
It's a horrible sight! (this form is a contraction of IT IS, and is never used as a possessive)
Its' (does not exist!)

Of course, there's always the problem of their/there/they're:

Their parents were gone all night. (possessive)
There were 100 people there. ("there" indicates a place, or with the verb "to be" to indicate existence)
They're in big trouble now! (this form is a contraction of THEY ARE)

The apostrophe can also be used to form a contraction of two words, as seen in the above examples. The apostrophe can take the place of ONE or TWO letters:

I am --> I'm
Do not --> don't
She will --> she'll

When making proper names plural, the apostrophe is never used:

The Smiths live here.
The Smith's live here.

The apostrophe can, however, be used to make letters and numbers plural:

Norman got all A's on his report card.
We studied the early 1900's today.

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ONE comma is used to separate ideas within a sentence. TWO commas are used to set off ideas; you should be able to remove what is between the commas and still have a complete sentence that makes sense.

ONE comma is used:

  1. Between items in a list:

    Don't forget to pick up bread, cheese, steaks, and milk. (4 items)
    Don't forget to pick up bread, cheese steaks, and milk. (3 items)

  2. Between adjectives:

    She wore a beautiful, luminous, extravagant wedding gown.

  3. Between independent clauses (meaning they can each stand as separate sentences) joined by a conjunction:

    Jim forgot to empty the garbage, and his mother wasn't happy about it.
    I called three times, but no one was home.
    Betty didn't make the cheerleading team, nor did she really want to.

  4. To introduce material separate from the subject:

    After eating, we played ball at the park.
    In my opinion, the world can do without corn dogs.
    If you kids don't stop fighting, I'll turn this car around right now!

TWO commas are used:

  1. When addressing people by name:

    Let's eat Grandma before it gets too late. (run, granny, run!!)
    Let's eat, Grandma, before it gets too late.

  2. To identify or define:

    Carol, my secretary, joined me for lunch yesterday.
    We tried Bingles, the new restaurant next door to our office, for a quick bite.

  3. When interrupting the sentence:

    Carlos Santana is, in my opinion, a great artist.
    He can't compare, however, to Jimi Hendrix.

  4. To set off unnecessary material:

    Tara's mother, who is a wonderful cook, baked brownies for our club.

    Note: Do not set off necessary material:

    Women who are pregnant should not smoke.
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To avoid comma splices (joining two complete sentences with a comma) and run-on sentences (not using punctuation to join parts of a sentence), the semicolon can be useful. Simply put, the semicolon joins two complete sentences that are closely related.

Comma splice: I don't like the circus, the clowns scare me.
Run-on: I don't like the circus the clowns scare me.
Correct: I don't like the circus; the clowns scare me.
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Page last updated: April 21, 2016